1. Field of the Invention
The present invention relates to stress reduction during welding. More specifically, the invention provides a method of stress relief wherein the component being welded is vibrated during welding to reduce stresses in the component.
2. Description of the Related Art
Welding is typically used to perform repairs on components of various equipment that is subject to harsh environments. One example is the repair of diaphragm shrouds for a combustion turbine by gas metal arc welding, micro-plasma welding, or gas tungsten arc welding. Such diaphragms are arranged in succession within the compressor of the turbine, with each successive diaphragm having an increasing number of vanes to further compress air being forced into the combustion chamber. Such diaphragms may be exposed to temperatures from room temperature to about 900° F. These diaphragms are difficult to repair, and expensive to replace. Presently available welding methods may produce significant distortion within the diaphragm, partly due to stresses created within the diaphragm from the welding process.
The use of vibrating a component being welded to reduce stress has been used for aluminum components in the past. However, vibration stress relief has not previously been used for the 410 or 403 stainless steels typically used for diaphragms, in part because appropriate vibration frequencies have not been developed. Stainless steel has a higher yield strength than other materials for which vibration stress relief has been used, increasing the difficulty of stress relief. The diaphragm and other stainless steel components of combustion turbines are very prone to distortion, making stress relief during repair of these components critical.
Accordingly, there is a need for a method of relieving stress within a component such as a combustion turbine diaphragm during weld repairs. There is a further need for the development of an appropriate frequency for using vibration stress relief upon components made from 410 stainless steel, 403 stainless steel, and other stainless steels.